All Reef Creatures Great and Small

In a follow up to our interview with Prof. Charles Sheppard about his latest expedition to the Chagos Archipelago, here is PhD researcher Catherine Head in an exclusive Seamonster guest post giving us a glimpse of the incredible hidden word of coral reef cryptofauna.

Chagos for me is what it’s all about, it represents why I choose to work in marine conservation and research. This British Indian Ocean Territory (BIOT) is remote and consequently working there is a great adventure, and most importantly for me the marine environment is as close to ‘pristine’ as you can get. Earlier this year I was lucky enough to be part of a 2-week Chagos scientific expedition around the archipelago (kindly funded by the Darwin Initiative) and see for myself why these reefs are considered some of the healthiest and most vibrant in the world.

Many of you are probably wondering where on earth this place is, well let me set the scene…find the Indian Ocean on a map follow your eyes down from the tip of Indian to a tiny dot near the Maldives, that’s the Chagos Archipelago.

This very remote archipelago is uninhabited, with the exception of a US military base on one of island, as a result it has extremely clean waters, resilient coral reefs, and coastal fish biomass in orders of magnitude larger than anywhere else in the Indian Ocean and perhaps the world.

In 2010 it was designated a marine protected area (MPA), and at 650,000 km2 it is currently the world’s largest no-take MPA, something that as a British citizen I am very proud of (Chagos is a British overseas territory). Of course there are challenges to managing a marine reserve roughly the size of France and predominantly open-ocean. To help tackle these problems Chagos has joined the Big Ocean Network, a network of the world’s largest MPAs that aims to improve global marine management efforts by sharing information, expertise and resources (see Chagos Trust).

This year I was in Chagos to study the diversity of the reef cryptofauna as part of my PhD. The cryptofauna are all those tiny creatures like shrimp, crabs, molluscs, and brittle stars which live in the nooks and crannies of the reef structure and do vital jobs such as breaking down all the dead organic matter that floats to the bottom. Mostly these creatures go unnoticed, partly because they are so tiny, and well-camouflaged (and believe me they can be a pain in the neck to sample!) but they are crucial to the functioning of the reef ecosystem, and are often compared to the insects in the rainforest in terms of their diversity and importance.

Most coral reef studies focus on the fish and coral but the cryptofauna actually makes up the largest component of reef biodiversity. I’m aiming to quantify this biodiversity (number of species, abundance and those kind of things), whilst also studying Chagos to look at how this component of biodiversity functions in the absence of direct human impact, and compare that to other areas in the Indian Ocean which are degraded as a result of human activities, such as overfishing, pollution, anchor damage etc.

We might find that like the fish and coral communities there is a higher biomass of the cryptofauna in healthy Chagos reefs, indicating that human disturbance has even more implications for coral reefs then previously thought. Or the opposite could be true that actually there is a lower diversity and abundance of the cryptofauna maybe because no fishing means there are larger fish populations preying on the cryptofauna. Either way it will increase our knowledge of how coral reef’s function in rare places like Chagos where there is no or minimal disturbance from humans, and I hope ultimately it will feed into understanding how we can better protect them.

Exploring Chagos waters and witnessing for myself the diversity of life they support has been a privilege and an inspiration. There are not many places where on just one dive you can lay your transect line on a nurse shark quietly resting amongst the abundant Acorpora coral tables, whilst keeping a careful eye on a very curious silver tip reef shark, and then moments later watch an eagle ray effortless guide across the reef, not to mention the thousands of reef fish swimming around! It really is a phenomenal place.